Antigenicity of rat collagen; reverse anaphylaxis induced in rats by anti-rat collagen serum.

Reverse anaphylactic shock was induced in rats by intravenous injection of serum containing complement-fixing antibodies, obtamed by immunization of rabbits with purified preparations of rat tail collagen. Normal rabbit serum or serum containing antibodies to collagen from tunica of carp swim bladder was without effect. The clinical and pathological findings resembled those described by previous workers studying direct and reverse anaphylactic reactions induced in the rat with other antigens. Thrombocytopenia, leukopenia with rebound leukocytosis, delayed blood coagulability, lowering of serum complement and the development of a refractory state to the antibody after the initial shock-all compatible with anaphylaxis-were demonstrated. The reacting substance was found to be in the gamma globulin fraction of the serum, and the antibody titer appeared to be correlated with the degree of shock and vascular injury. Collagen injury in rats dying from acute shock or in those injected with repeated sublethal doses was not demonstrated by the methods employed; techniques by which lesions of collagen might be induced are discussed. Absorption experiments indicated that anti-rat collagen rabbit serum is specifically directed to a substance, apparently collagen, in the rat; it is likely that the combination of the antibody and collagen induces anaphylactic shock. These studies, made in vivo, provide further evidence of antigenic and immunological differences between acid-soluble rat and fish collagens.